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R W Padgett

Publications and source records attributed to R W Padgett.

At least 37 records · Page 2Linked to original sources
PubMed1996

Caenorhabditis elegans genes sma-2, sma-3, and sma-4 define a conserved family of transforming growth factor beta pathway components.

Although transforming growth factor beta (TGF-beta) superfamily ligands play critical roles in diverse developmental processes, how cells transduce signals from these ligands is still poorly understood. Cell surface receptors for these ligands have been identified, but their cytoplasmic targets are unknown. We have identified three Caenorhabditis elegans genes, sma-2, sma-3, and sma-4, that have mutant phenotypes similar to those of the TGF-beta-like receptor gene daf-4, indicating that they are required for daf-4-mediated developmental processes. We show that sma-2 functions in the same cells as daf-4, consistent with a role in transducing signals from the receptor. These three genes define a protein family, the dwarfins, that includes the Mad gene product, which participates in the decapentaplegic TGF-beta-like pathway in Drosophila [Sekelsky, J. J., Newfeld, S. J., Raftery, L. A., Chartoff, E. H. & Gelbart, W. M. (1995) Genetics 139, 1347-1358]. The identification of homologous components of these pathways in distantly related organisms suggests that dwarfins may be universally required for TGF-beta-like signal transduction. In fact, we have isolated highly conserved dwarfins from vertebrates, indicating that these components are not idiosyncratic to invertebrates. These analyses suggest that dwarfins are conserved cytoplasmic signal transducers.

Amino Acid Sequence↗
PubMed1996

The Drosophila decapentaplegic and short gastrulation genes function antagonistically during adult wing vein development.

TGF-beta-related signaling pathways play diverse roles during vertebrate and invertebrate development. A common mechanism for regulating the activity of TGF-beta family members is inhibition by extracellular antagonists. Recently, the Drosophila short gastrulation (sog) gene was shown to encode a predicted diffusible factor which antagonizes signaling mediated by the TGF-beta-like Decapentaplegic (Dpp) pathway in the early blastoderm embryo. sog and dpp, which are among the earliest zygotic genes to be activated, are expressed in complementary dorsal-ventral domains. The opposing actions of sog and dpp in the early embryo have been highly conserved during evolution as their vertebrate counterparts, chordin and BMP-4, function homologously to define neural versus non-neural ectoderm in Xenopus. Here we exploit the genetically sensitive adult wing vein pattern to investigate the generality of the antagonistic relationship between sog and dpp. We show that dpp is expressed in vein primordia during pupal wing development and functions to promote vein formation. In contrast, sog is expressed in complementary intervein cells and suppresses vein formation. sog and dpp function during the same phenocritical periods (i.e. 16-28 hours after pupariation) to influence the vein versus intervein cell fate choice. The conflicting activities of dpp and sog are also revealed by antagonistic dosage-sensitive interactions between these two genes during vein development. Analysis of vein and intervein marker expression in dpp and sog mutant wings suggests that dpp promotes vein fates indirectly by activating the vein gene rhomboid (rho), and that sog functions by blocking an autoactivating Dpp feedback loop. These data support the view that Sog is a dedicated Dpp antagonist.

Animals↗
PubMed1996

The TGF-beta signaling pathway is essential for Drosophila oogenesis.

We examine roles of signaling by secreted ligands of the TGF-beta family during Drosophila oogenesis. One family member, the DPP ligand encoded by the decapentaplegic (dpp) gene, is required for patterning of anterior eggshell structures. This requirement presumably reflects the expression pattern of dpp in an anterior subset of somatic follicle cells: the centripetally migrating and the nurse cell-associated follicle cells. Similar requirements are also revealed by mutations in the saxophone (sax)-encoded receptor, consistent with the idea that DPP signaling is, at least in part, mediated by the SAX receptor. A loss of germline sax function results in a block in oogenesis associated with egg chamber degeneration and a failure of the transfer of nurse cell contents to the oocyte, indicating that TGF-beta signaling is required for these events. Some phenotypes of sax mutations during oogenesis suggest that SAX responds to at least one other TGF-beta ligand as well in the posterior follicle cells.

Actins↗
PubMed1995

The tolkin gene is a tolloid/BMP-1 homologue that is essential for Drosophila development.

The Drosophila decapentaplegic (dpp) gene, a member of the transforming growth factor beta superfamily of growth factors, is critical for specification of the embryonic dorsal-ventral axis, for proper formation of the midgut, and for formation of Drosophila adult structures. The Drosophila tolloid gene has been shown to genetically interact with dpp. The genetic interactions between tolloid and dpp suggests a model in which the tolloid protein participates in a complex containing the DPP ligand, its protease serving to activate DPP, either directly or indirectly. We report here the identification and cloning of another Drosophila member of the tolloid/bone morphogenic protein (BMP) 1 family, tolkin, which is located 700 bp 5' to tolloid. Its overall structure is like tolloid, with an N-terminal metalloprotease domain, five complement subcomponents C1r/C1s, Uegf, and Bmp1 (CUB) repeats and two epidermal growth factor (EGF) repeats. Its expression pattern overlaps that of tolloid and dpp in early embryos and diverges in later stages. In larval tissues, both tolloid and tolkin are expressed uniformly in the imaginal disks. In the brain, both tolloid and tolkin are expressed in the outer proliferation center, whereas tolkin has another stripe of expression near the outer proliferation center. Analysis of lethal mutations in tolkin indicate it is vital during larval and pupal stages. Analysis of its mutant phenotypes and expression patterns suggests that its functions may be mostly independent of tolloid and dpp.

Amino Acid Sequence↗
PubMed1994

The Drosophila saxophone gene: a serine-threonine kinase receptor of the TGF-beta superfamily.

The Drosophila decapentaplegic (dpp) gene encodes a transforming growth factor-beta (TGF-beta)-like protein that plays a key role in several aspects of development. Transduction of the DPP signal was investigated by cloning of serine-threonine kinase transmembrane receptors from Drosophila because this type of receptor is specific for the TGF-beta-like ligands. Here evidence is provided demonstrating that the Drosophila saxophone (sax) gene, a previously identified female sterile locus, encodes a TGF-beta-like type I receptor. Embryos from sax mothers and dpp embryos exhibit similar mutant phenotypes during early gastrulation, and these two loci exhibit genetic interactions, which suggest that they are utilized in the same pathway. These data suggest that sax encodes a receptor for dpp.

Amino Acid Sequence↗
PubMed1994

Mutational analysis of the Drosophila tolloid gene, a human BMP-1 homolog.

Seven zygotically active genes have been identified in Drosophila that determine the fate of dorsal cells in the developing embryo. decapentaplegic (dpp), a member of the transforming growth factor-beta (TGF-beta) family, appears to play the central role in dorsal ectoderm formation, as mutations in this gene confer the most severe mutant phenotype of this group of genes. dpp's activity is modulated by tolloid, which also has a role in the determination of dorsal cell fate. tolloid encodes a protein that contains a metalloprotease domain and regulatory domains consisting of two EGF motifs and five C1r/s repeats. We have generated several mutant tolloid alleles and have examined their interaction with a graded set of dpp point alleles. Some tolloid alleles act as dominant enhancers of dpp in a trans heterozygote, and are therefore antimorphic alleles. However, a tolloid deficiency shows no such genetic interaction. To characterize the nature of the tolloid mutations, we have sequenced eighteen tolloid alleles. We find that five of the seven alleles that act as dominant enhancers of dpp are missense mutations in the protease domain. We also find that most tolloid alleles that do not interact with dpp are missense mutations in the C-terminal EGF and C1r/s repeats, or encode truncated proteins that delete these repeats. Based on these data, we propose a model in which the tolloid protein functions by forming a complex containing DPP via protein-interacting EGF and C1r/s domains, and that the protease activity of TOLLOID is necessary, either directly or indirectly, for the activation of the DPP complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1993

Human BMP sequences can confer normal dorsal-ventral patterning in the Drosophila embryo.

The type beta transforming growth factor family is composed of a series of processed, secreted growth factors, several of which have been implicated in important regulatory roles in cell determination, inductive interactions, and tissue differentiation. Among these factors, the sequence of the DPP protein from Drosophila is most similar to two of the vertebrate bone morphogenetic proteins, BMP2 and BMP4. Here we report that the human BMP4 ligand sequences can function in lieu of DPP in Drosophila embryos. We introduced the ligand region from human BMP4 into a genomic fragment of the dpp gene in place of the Drosophila ligand sequences and recovered transgenic flies by P-element transformation. We find that this chimeric dpp-BMP4 transgene can completely rescue the embryonic dorsal-ventral patterning defect of null dpp mutant genotypes. We infer that the chimeric DPP-BMP4 protein can be processed properly and, by analogy with the action of other family members, can activate the endogenous DPP receptor to carry out the events necessary for dorsal-ventral patterning. Our evidence suggests that the DPP-BMP4 signal transduction pathway has been functionally conserved for at least 600 million years.

Amino Acid Sequence↗
PubMed1993

Cross regulation of decapentaplegic and Ultrabithorax transcription in the embryonic visceral mesoderm of Drosophila.

The Drosophila decapentaplegic gene (dpp) encodes a TGF-beta family member involved in signal transduction during embryonic midgut formation. The shortvein (shv) class of cis-regulatory dpp mutants disrupt expression in parasegments 4 and 7 (ps4 and ps7) of the embryonic visceral mesoderm (VM) surrounding the gut and cause abnormalities in gut morphogenesis. We demonstrate that cis-regulatory elements directing expression in ps4 and ps7 are separable and identify DNA fragments that generate ps4 and ps7 expression patterns using reporter gene constructs. dpp reporter gene expression in both ps4 and ps7 is autoregulated as it requires endogenous dpp+ activity. Reporter gene ps7 expression requires the wild-type action of Ultra-bithorax (Ubx), and abdominal-A. Furthermore, the expression of certain Ubx reporter genes is coincident with dpp in the VM. Both the mis-expression of Ubx reporter genes in the developing gastric caecae at ps4 and its normal expression in ps7 are dependent upon endogenous dpp+ activity. We conclude that dpp both responds to and regulates Ubx in ps7 of the visceral mesoderm and that Ubx autoregulation within this tissue may be indirect as it requires more components than have previously been thought.

Animals↗
PubMed1991

Treatment-resistant depression: a survey of practice habits of Canadian psychiatrists.

Treatment-resistant depression is a fascinating yet poorly defined condition. The various management strategies in use are a source of controversy. The objective of this survey was to determine how Canadian psychiatrists treat patients with "intractable depression." This information may be used to plan future research into the management of treatment-resistant depression. It may also provide information about the practices of Canadian psychiatrists and help direct residency training. Confidential questionnaires were mailed to all psychiatrists residing in Canada registered with the Canadian Psychiatric Association. Respondents indicated that 12.4% of their depressed patients were "resistant to treatment." Respondents were asked to rank a list of treatment choices in the order they would use them to treat patients with treatment-resistant depression. Ninety-five point eight percent of respondents used tricyclics as the first treatment of choice. Almost equal portions of respondents chose a second tricyclic, a monoamine oxidase inhibitor (MAOI) or a combination of lithium and tricyclics as their treatment of second choice.

Antidepressive Agents↗
PubMed1990

Molecular organization of the decapentaplegic gene in Drosophila melanogaster.

The decapentaplegic (dpp) locus of Drosophila melanogaster is a greater than 55 kb genetic unit required for proper pattern formation during the embryonic and imaginal development of the organism. We have proposed that these morphogenetic functions result from the action of a secreted transforming growth factor-beta (TGF-beta)-related protein product encoded by dpp. In this paper we localize 60 mutations on the molecular map of dpp. The positions of these mutations cluster according to phenotypic class, identifying the locations of specific dpp functions. By Northern and cDNA analysis, we characterize five overlapping dpp transcripts. On the basis of the locations of the overlaps relative to a previously sequenced cDNA, it is likely that these transcripts all encode similar or identical polypeptides. We propose that the bulk of dpp DNA consists of extensive arrays of cis-regulatory information. The large (greater than 25-kb) 3' cis-regulatory region represents a novel feature of dpp gene organization

Alleles↗
PubMed1988

The F-type 5' motif of mouse L1 elements: a major class of L1 termini similar to the A-type in organization but unrelated in sequence.

It has previously been shown that the L1 family in the mouse (L1Md) contains two alternative 5' ends called the A- and F-type sequences (1,2). We show here that the F-type element is a major class of murine L1 elements and report on the details of organization of the 5' motif of these F-type elements. Although the A- and F-type 5' sequences share no detectable sequence homology the organization of an F-type 5' end is strikingly similar to that of an A-type. That is, the F-type 5' sequences consist of a tandem array of a small number of 206 bp monomers while the A-type 5' motif consists of a tandem array of 208 bp monomers. All of the A-type elements characterized to date have a truncated monomer at the 5' end of the array. Many of the F-type elements are also terminated at the 5' end by a truncated copy but unlike the A-type elements some F-type elements terminate with a monomer which is within a few nucleotides of being complete. In addition the F-type consensus sequence, in contrast to the A-type sequence, shows homology (70%) to the body of the L1Md starting at the position where the monomer joins the rest of the L1 element.

Animals↗
PubMed1987

The molecular organization of the beta-globin complex of the deer mouse, Peromyscus maniculatus.

Recombinant DNA clones have been isolated that contain 80 kb of the beta-globin complex from the deer mouse, Peromyscus maniculatus. Comparisons of this complex with that from the laboratory mouse, Mus domesticus (with an order 5'-Hbby, Hbb-bhO, Hbb-bhl, Hbb-bh2, Hbb-bh3, Hbb-bl, Hbb-b2 3') highlight organizational trends in the beta-globin complex since the two species diverged. Unlike other mammals studied thus far, the deer mouse possesses three adult genes. Partial sequence analysis indicates that each of the three adult genes is intact and hence may be functional. Hybridization of one of the two Mus pseudogenes, Hbb-bh3, to genomic blots from Peromyscus reveals that it has a homologous counterpart in Peromyscus. Homologous genes to the two gamma-like Mus genes, Hbb-bhO and Hbb-bhl, are also found in Peromyscus. The strong hybridization between the Hbb-bhl genes and significant nucleotide similarity between the Hbb-bhO genes suggest that both pairs are important for the ontogeny of these mice although no known product has been identified for the Hbb-bhO genes. The presence of Hbb-bhO and Hbb-bhl in Peromyscus suggests that the duplication that created this related gene set occurred before the two lineages diverged. A single gene for Hbb-y has been isolated from Peromyscus. The adult region in Peromyscus has undergone significant divergence from the same region in Mus, having three rather than two adult genes, the acquisition of at least 15 kb of extra DNA relative to Mus, and possibly the loss of the Hbb-bh2 pseudogene. The nonadult region of the complex, in contrast, contains the same set of genes apparently distributed over the same amount of DNA as in the Mus beta-globin complex. This observation suggests that the embryonic region of the complex is more evolutionarily stable than the adult region.

Animals↗
PubMed1986

The sequence of a large L1Md element reveals a tandemly repeated 5' end and several features found in retrotransposons.

The complete nucleotide sequence of a 6,851-base pair (bp) member of the L1Md repetitive family from a selected random isolate of the BALB/c mouse genome is reported here. Five kilobases of the element contains two overlapping reading frames of 1,137 and 3,900 bp. The entire 3,900-bp frame and the 3' 600 bp of the 1,137-bp frame, when compared with a composite consensus primate L1 sequence, show a ratio of replacement to silent site differences characteristic of protein coding sequences. This more closely defines the protein coding capacity of this repetitive family, which was previously shown to possess a large open reading frame of undetermined extent. The relative organization of the 1,137- and 3,900-bp reading frames, which overlap by 14 bp, bears resemblance to protein-coding, mobile genetic elements. Homology can be found between the amino acid sequence of the 3,900-bp frame and selected domains of several reverse transcriptases. The 5' ends of the two L1Md elements described in this report have multiple copies, 4 2/3 copies and 1 2/3 copy, of a 208-bp direct tandem repeat. The sequence of this 208-bp element differs from the sequence of a previously defined 5' end for an L1Md element, indicating that there are at least two different 5' end motifs for L1Md.

Amino Acid Sequence↗
PubMed1984

The mouse globin pseudogene beta h3 is descended from a premammalian delta-globin gene.

The beta h3 pseudogene of the BALB/c mouse contains sequence defects which prevent transcription and translation to produce a beta-globin. Comparison with other globin gene sequences indicates that beta h3 arose by recombination between an adult beta-globin gene and some significantly diverged globin sequence. Analysis of noncoding sequences shows that the 3' end of mouse beta h3 and the human delta-globin gene are both descended from an ancestral gene, which we call proto-delta. The origin of proto-delta must predate the mammalian radiation. A member of the L1 family of interspersed repetitive elements is inserted into the 3' untranslated delta-homologous sequence in beta h3 from BALB/c. beta h3 is a widespread feature of the rodent beta-globin complex, which has been fixed in the genome for 35 million years. Independent inactivation events produced pseudogenes located between the adult and nonadult beta-globin genes in the rodent, primate, rabbit, and goat lineages. One model to explain the abundance and evolutionary persistence of pseudogenes postulates that the mammalian genome simply has no efficient mechanism for deleting nonessential sequences. Consequently, the genomes of higher eukaryotes have been growing, by the accumulation of duplications, with doubling times of 200 +/- 100 million years.

Animals↗
PubMed1984

Molecular cloning and sequence analysis of a cDNA coding for the mouse alpha-like embryonic globin chain x.

Cytoplasmic poly(A)+mRNA from 12-day mouse-yolk-sac erythroid cells has been used to prepare a cDNA library in the plasmid pBR322. One clone containing sequences coding for the alpha-like embryonic globin chain x, pHE52, has been identified by hybrid selection and in vitro translation of the complementary mRNA. The nucleotide sequence of pHE52 confirms that it codes for an embryonic alpha-like globin chain. The insert sequence is 316 nucleotides long, contains the codons corresponding to amino acid residues 43-141, and extends into the 3' untranslated region. An analysis of the nucleotide sequence of pHE52 and the other known alpha globins suggests that the adult-embryonic divergence began approx. 400 million years ago reflecting a difference in the evolutionary history of the alpha- and beta-globin gene complexes.

Amino Acid Sequence↗
PubMed1982

beta-globin transcript found in induced murine erythroleukemia cells is homologous to the beta h0 and beta h1 genes.

RNA transcripts complementary to at least one of the four beta-globin homologous genes (beta h) are found in high concentration in the murine erythroleukemic (MEL) cell line GM979 after butyric acid induction. Hybridization data indicate that the gene expressed is Hbb-beta h0 or Hbb-beta h1, or both. The level of beta h0/1 transcripts in the MEL cell is similar to the level of adult transcripts. The Hbb-beta h0/1 transcript is about 800 nucleotides in length. In addition, there is a larger beta h0/1 transcript of the same size and relative intensity as the adult beta-globin precursor. We also report significant levels of embryonic gene Hbb-y transcripts in induced GM979 cells. We have determined that the GM979 cell line has the [Hbb]s haplotype on the basis of an examination of its globin DNA restriction pattern. An additional MEL cell line of haplotype [Hbb]d (DBA/2 line 6A11A) was examined and found to contain no significant level of Hbb-beta h0, Hbb-beta h1, Hbb-beta h2, or Hbb-y gene transcripts.

Animals↗